Magnesium alloy and method of making same



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MAGNESIUM ALLOY AND METHOD OF MAKING SAME.

We Drawing.

The present improved alloy is one in which magnesium is the predominantelementfthe' object being to develop an alloy that will possess thecharacteristic lightness i'which is obtained by the use of magnesiumtin-excess of,80 per cent, while such alloy will be characterized-byhigh strength and toughness as well as by having a fine grainedstructure when cast in the usual manner.

So far as I am aware, it has not heretofore been found feasible to heatthe metals in question together for the purpose of alloying the samesince this will presumably involve the use of a temperature above theboiling point of magnesium. By the present improved method, however, ithasbeen found possible to produce alloys of these two metals containingsubstantial amountsof chromium. corresponding with the amount forinstance employed in various commercial steels in which chromium is 'aneffective ingredient and exercising a marked influence in the resultantproduct. Such product having a a chromium content of less than 1 percent is for all practical purposes no heavier than pure magnesium whichof course is very much lighter than aluminum and the commercial'aluminum alloys; at the same'time, if properly cast, such alloy is ofconsiderable greater tensile strength and impact-toughness withoutbeing-pnduly hard, while at the same time it possesses, as noted above,an

unusually fine grained structure when'made I up in the form of acasting, I

The invention, then, consists of a new product containing magnesium. andchromium in approximately the proportions indicated, together with thesteps involved in the making of such alloys hereinafter fully describedand particularly set forth in the claims. The following description, itwill be understood, thus sets forthbut one of the various ways in whichthe principle of the invention may be carried out.

Briefly. stated, the improved. method of making the alloy in handconsists in interfusing a limited amount of a suitable chromium compoundwith an excess of magnesium, whereby such compound is reduced to themetal and thereupon fprms an alloy with the residuum of magnesium stilllargely exceeding the amount of the chromium thus reduced from thecompound employed. Preferably chromium sesquioxide, C501, is

employed, although anhydrous chromic chlo- Y By the foregoing method Ihave succeeded r10 Application filed December 19, 19%. Serial No.757,035.

ride, (lrCl may be utilized. The latter may be conveniently prepared byevaporatin a solution of the normal. chloride to a thick viscous syrup.This thick mass is then heated in an atmosphere of dry hydrochloric acidgas, whereupon the material swells to'many times its original bulk andgradually changes in color from green to pink, the final product beingvery light and fluffy.

For the purpose of introducing the chromium, a mass. of molten magnesiumis first prepared preferably usinga flux of slightly greater specificgravity than the molten metal and having a sufiicient surface tension tocause it to form a film thereover and thus prevent exposure of the metalto the atmosphere. The chromium oxide, or chloride, as the case may be,is then added to such molten magnesium, the coating of flux on thelatter being pushed aside so as to permit such oxide to come directlyinto contact with the metallic surface of the magnesium since it theoxide becomes wetted with the flux, it does not react or at least reactreadily. If necessary, a thorough inter-mixture of the oxide with themolten magnesium may be insured by stirring. However, the reaction ofthe magnesium. with the oxide occurs almost immediately, the latterbeing reduced to metallic form and incorporated in' the mass of moltenmagnesium to form the de sired alloy.

The molten alloy may then be conveniently removed from the crucible ormelting pot by means of an ordinary ladle and is cast into bars or suchother shapes as may be desired. The theoretical amount of chromiumderived from any given quantity of the oxide may of course be readilycalculated, but some of this apparently is lost in the reaction, atleast less than the theoretical amount of chromium appears in the finalalloy. However, the amount of oxide that requires to be added to thegiven alloy containing the desired number of hundredths per cent ofchromium may be determined by deducting such loss in the theoreticalamount as may be encountered in practice, all of which will be readilyunderstood by anyone skilled in such matters. The amount of suchalloying ingredient actually introduced may be checked by analysis,using the method ordinarily employed in the analysis of chrome-vanadiumsteel.

in combining as much as eight-hundredths (0.08) per cent of chromiumwith magnesium. In taking samples of this alloy, the metal comes. off inlong ribbons instead of breaking into chips under the drill aspuremagnesium does and in other respects, as hereinbefore set forth, amarked improvement in structure and physical qualities is obtained. Ihave also found it possible to add metallic chromium directly to moltenmag nesium by heating the former with the latter in an iron crucible fora sufficient time, for example a half hour, and stirring with an ironrod: In order to clear the resultant alloy from occlusions'of flux andfrom. particles of the chromium that have not become properly alloyed,it is desirable to re-melt such alloy one or more times. By this methodI have likewise obtained an alloy containing as high as eight-hundredths(0.08) per cent of chromium.

It will be understood that the foregoing method using chromium oxidewith an excess of metallic magnesium, whereby the oxide is reduced tometal and thereby incorporated to form the desired alloy, is alsoapplicable to the preparation of other alloys of magnesium with othermetals of the chromium group. 1

Ot er modes of applying the principle of my invention may be employedinstead of the one explained, change being'made as regards thecomposition and method herein disclosed, provided the ingredients orsteps stated by any of the following claims or the equivalent of suchstated steps be employed.

I therefore particularly point out and distinctly claim as myinvention':--

1. As a new product, an alloy of magnesium with from one one-hundredthfto onetenth of one per cent of chromium.

2. As a new product, an alloy consisting of magnesium and a substantialamount but less than one tenth of one per cent of chromium. V

3. As a new product, an alloy consisting of magnesium and betweenapproximately one one-hundredth and one-tenth of one per cent ofchromium.

4. The 'method of making an alloy of chromium with magnesium whichconsists infusing into an excess of magnesium a small amount of achromium compound to be reduced to metallic state by magnesium.

5. The method of making an alloy of chromium with magnesium, whichconsists in interfusing a'limited amount of chromium oxide in an excessof magnesium.

6. The method of making an'alloy of chromium with magnesium, whichconsists in adding to a body of magnesium in molten .state a smallamount of a chromium compound adapted to be reduced to metallic state bythe magnesium the amount of magnesium being'considerably in excess ofthat required to'reduce such compound, whereby the desired proportion ofchromium is'incorporated.

7. The methodxof making an alloy of chromium with magnesium, which 7consists in adding a limited amount of chromium oxide to a body ofmagnesium in molten state, the amount of magnesium beingconsiderably inexcess of that required to reduce such oxide, whereby the desiredproportion of chromium is incorporated; v

Signed by me this 17th day of December,

1924.. WILLIAM R. VEAZEY.

